By Joe D'Aleo
Monday, March 9, 2009
The sun continues in hibernation mode. NASA and others thought in late 2006 it had bottomed out but it has continued to slide. Since it can’t go negative, it has leveled off scraping the bottom of the chart. The NASA team projections for the next cycle continue to slip further into the future and periodically adjusted down. They present two scenarios one for a more active cycle (24) with a peak at the start of 2012 and the second a weaker one peaking around the end of 2012 or start of 2013.
When will the minimum be? Since the most common method is the 13 month running mean. You don’t know for sure when a minimum takes place sometimes until 6 months after it occurs. The exception would be a month with a very big jump (Much higher than 13 months ago). That would indicate the mean 7 months ago will turn up, at least a relative minimum. With the February sunspot number lower than 13 months ago, the minimum can’t be earlier than August 2008 and more likely October 2008. It could be later. That would make the cycle 23 length at least 12 years 5 months long. That would be the longest since the middle 1800s and perhaps the late 1700s or early 1800s.
There are many scientists who believe cycle 24 will be far less active than either NASA projection. Some use cycle length and the behavior of certain types of activity like the geomagnetic activity at the minimum as indicators. Like the climate and ENSO forecast models, some models are statistical others dynamical. See some projections here.
They include Clilverd et al who believes based on regression analysis a very quiet cycle like the early 1800s. He states:
“We use a model for sunspot number using low-frequency solar oscillations, with periods 22, 53, 88, 106, 213, and 420 years modulating the 11-year Schwabe cycle, to predict the peak sunspot number of cycle 24 and for future cycles, including the period around 2100 A.D. We extend the earlier work of Damon and Jirikowic (1992) by adding a further long-period component of 420 years.
Typically, the standard deviation between the model and the peak sunspot number in each solar cycle from 1750 to 1970 is ±34. The peak sunspot prediction for cycles 21, 22, and 23 agree with the observed sunspot activity levels within the error estimate. Our peak sunspot prediction for cycle 24 is significantly smaller than cycle 23, with peak sunspot numbers predicted to be 42 ± 34.
These predictions suggest that a period of quiet solar activity is expected, lasting until around 2030, with less disruption to satellite orbits, satellite lifetimes, and power distribution grids and lower risk of spacecraft failures and radiation dose to astronauts. Our model also predicts a recovery during the middle of the century to more typical solar activity cycles with peak sunspot numbers around 120.
Eventually, the superposition of the minimum phase of the 105- and 420-year cycles just after 2100 leads to another period of significantly quieter solar conditions. This lends some support to the prediction of low solar activity in 2100 made by Clilverd et al. 2003.”
The number of sunspotless days this cycle transition at the end of February had totaled 559. This year through the end of February already has had 49 days and may break into the top 12. It is shown on the chart although there are other years with between 49 and 159 days.
Sunspotless days per year since 1849 (adapted from Solaemon’s Sunpotless Days Page)
The Geomagnetic Index (Ap) also continues extraordinarily low.
This has resulted in a very low level of aurora activity. As this Newsminer story noted:
“The Interior’s normal wintertime light show has been noticeably absent this winter. “I talk to people in town and everybody who knows what I do asks me, ‘Where is the aurora? What’s happening?’” said Dirk Lummerzheim, a research professor who studies the aurora borealis for the Geophysical Institute at the University of Alaska Fairbanks. It’s a legitimate question, and Lummerzheim has the answer. “We are at the solar minimum,” the UAF professor said. “When solar activity dies down like this, the aurora activity also diminishes in the north.” Aurora borealis, a curtain-like, luminous glow in the upper atmosphere, is caused when energy particles from the sun collide with the Earth’s magnetic field. Solar activity runs on a 22-year cycle - 11 positive years and 11 negative years. The cycle is at the bottom of the negative cycle, Lummerzheim said. This is the second winter in a row the aurora has been “quiet,” as Lummerzheim put it. Normally, the low in the solar cycle only lasts about a year, he said. Lummerzheim described the current solar minimum as “very long, very deep.” “I think the last time we had a minimum this low was early in the 20th century,” he said.
Aurora scholar Neal Brown, who directs UAF’s Alaska Space Grant Program, said the low in the current solar cycle is the most dramatic he has witnessed during his time in Fairbanks. “I’ve lived here for 45 years, and we’ve had four solar cycles, and this is the worst one for me,” Brown said. “It’s just been pitiful. I don’t think there’s been three or maybe four half-hour to hour-long displays this winter.”
The lack of an aurora has not been lost on businesses that cater to aurora viewers, specifically the hundreds of Japanese tourists who flock to Alaska each winter on direct flights from Japan to see the northern lights. “It hasn’t been as good a year as usual,” said Jenny Kirsch, assistant general manager at Chena Hot Springs Resort, a popular aurora viewing spot for many of the tourists. “Colors are hard to find.” Mok Kumagai at Aurora Borealis Lodge on Cleary Summit agreed. The aurora displays during the past two winters have been weak, he said. “
NASA’s Hathaway had projected an active cycle 24. He was part of a NOAA/NASA team that projected the upcoming cycle. They were divided among those who expected an active and those who expected a quieter cycle. Hathaway was in the active group but to his credit has backed off and in 2006 had noted that quieter cycles wee ahead. He projected cycle 25 peaking after 2020, could be the quietest in centuries. That may be true, cycle 24 may be close. Livingston and Penn found the sunspots have been fading (diminishing contrast with surrounding solar surface) through recent cycles.
A linear fit to observed magnetic fields extrapolated to the minimum value observed for umbral magnetic fields; below a field strength of 1500G as measured with the Fe I 1564.8nm line no photospheric darkening is observed. More recent data points continue along the trend line (not shown). A linear fit would mean sunspots would appear to vanish by 2015.
Based on the forecast Dalton like minimum, Archibald has projected a colder globe in decades ahead. Here he projects the effect on agriculture.